GB2196717A - Fender - Google Patents

Abstract

A fender such as a ship's fender or sponson (F) is composed of a thick layer (1) of compressible foam with an outer coating (2) of shock- absorbing elastomeric material defining an envelope containing air or gas at substantially atmospheric presaure. The inner layer (1) may be of closed cell polyethylene foam, and the outer layer (2) of polyurethane. <IMAGE>

Description

SPECIFICATION Fender This invention relates to a fender, and in particular to a fender for ships and boats.

Fenders are used extensively in marine applications, both on ships and boats and at mooring points. Traditionally, fenders are used to protect ships, boats and fixed installations from the worst effects of impacts. Recently, however, fenders have been incorporated in vessels known as rigid inflatable boats (RIBs).

An RIB has a rigid hull and an inflatable collar supported by the hull. The inflatable collar acts as a fender to protect the boat against impacts, and also to give added buoyancy. It also helps to give a softer ride at high speeds, as it tends to damp out the forces transmitted to the hull by the impact of waves. Typically, such a collar (known as a sponson) is made of a rubber-coated fabric, a polymer-coated woven fabric, or a thermal plastic polymer filled with pressurised air.

Known sponsons suffer from the disadvantage that punctures lead to a loss of their buoyancy and impact-protecting properties. Moreover, air temperature changes effect the pressure within such sponsons, and this hasan undesirable effect on their performance in adverse sea states. Thus, a sponson which is subjected to over-pressure leads to excessive banging when the RIB is running at an angle to the sea state. Conversely, if the sponson pressure is too low, the RIB tends to fall further into an impacting wave, and both stability and boat handling become problems.

The aim of the invention is to provide a fender (sponson) which does not suffer from these disadvantages.

The present invention provides a fender constituted by a closed envelope filled with a gas at substantially atmospheric pressure, the envelope being made of a laminated material which comprises an outer layer made of a hard, resilient, shock-absorbing material and an inner layer made of a compressible, shockwave-damping material.

The outer layer of this fender constitutes the primary shock absorber, whilst the inner layer damps out any dangerous shock waves which pass through the outer layer. Any residual shock waves are then dissipated by the gas filling.

Advantageously, the outer layer is relatively thin, and the inner layer is relatively thick. preferably, the inner layer is made of a closed cell foam material, such as a memory polyethylene foam, and the outer layer is made of an elastomer material such as a polyurethane elastomer. Normally, the gas is air.

The envelope may have a generally annular crosssection, and the fender may further comprise a plurality of longitudinally-spaced, transverse baffles positioned within the envelope. Advantageously, the baffles are made of the same material as the inner layer.

In a preferred embodiment, the fender further comprises fixing straps for fixing the fender to a structure to be protected against impacts, the fixing straps being encapsulated within the outer layer. In this case each of the fixing straps may be positioned to overlie a respective baffle.

The invention also provides a method of making a fender, having a closed envelope filled with a gas at substantially atmospheric pressure, the method comprising the steps of forming an inner envelope layer made of a compressible shock-wave-damping material, filling the inner envelope layer with a gas at the required pressure, and bonding an outer envelope layer to the inner envelope layer, the outer envelope layer being made of a hard, resilient, shock-absorbing material.

Advantageously, the inner layer is formed in cylindrical sections from a closed cell foam material, the sections being heat-sealed or bonded together. Preferably, each of said sections is made by bending a sheet of closed cell foam material around a former, and by heat-sealing or bonding the edges of the sheet together. In this case, the method may further comprise the step of heat sealing or bonding longitudinally-spaced, transverse baffles within the inner layer, the baffles being made of the same material as the inner layer.

Conveniently, the outer layer is an elastomer which is sprayed onto the inner layer. Preferably, the method further comprises the step of encapsulating fixing straps within the outer layer, the outer layer being formed from a plurality of sprayed-on coats, and the straps being positioned between two adjacent sprayedon coats.

A fender constructed in accordance with the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of an RIB incorporating the fender, shown in the water; Fig. 2 is a transverse cross-section through the fender; Fig.3 is a longitudinal cross-section through the fender; Fig. 4 is a transverse cross-section of a modified fender; and Fig. 5 is a side elevation of a conventional vessel using the modified fender shown in Fig.

4 Referring to the drawings, Fig. 1 shows an RIB having a hull H attached to a fender (sponson) F. The fender F has a circular cross-section (see Fig. 2) and is constituted by an annular layer 1 of polyethylene closed cell foam covered with a coating 2 of polyurethane elastomer. The central region of the fender F is filled with air at atmospheric pressure.

As shown in Fig. 3, the fender F is strengthened by a series of baffles 3, these baffles also being made of polyethylene closed cell foam. The fender F is attached to the hull H by means of nylon fixing straps 4, aluminium fixing plates 5 and bolts (not shown), the fix ing plates being attached to the ends of the fixing straps which are encapsulated within the elastomer coating 2. The fixing straps 4 are positioned to overlie the baffles 3 (see Fig. 3).

The fender F is constructed in the following manner. Firstly, the annular layer 1 is made from a plurality of annular sections, Each sec tion is formed from a sheet of polyethylene closed cell foam by bending the sheet round a cylindrical former, and by fixing the ends thereof together, either by heat sealing or by a suitable adhesive. The annular sections are joined together, either by heat sealing or by a suitable adhesive, to form the annular layer 1.

prior to this step, the baffles 3 (which are also formed from sheets of polyethylene closed cell foam) are fixed within some or all of the sections. Here again, the fixing is either by heat sealing or by adhesive. The layer 1 of foam is then covered with the elastomer coating 2. This coating 2 is applied by spraying on a plurality (typically six) layers of elastomer material. After two or three layers have been sprayed on, the nylon fixing straps 4 are placed in position over the baffles 3, and the remaining layers of elastomer are then sprayed on. This results in the fixing straps 4 being firmly encapsulated in the elastomer coating 2.

The fixing plates 5 are then fixed to the ends of the straps 4, so that the fender F is ready for fixing to the hull H.

The fender F shown in Figs. 1 to 3 will have dimensions adapted to the boat concerned. Typically, it will have a diameter of about 1 5 inches, the thickness of the layer 1 will be about 1.5 inches, the thickness of the elastomer coating 2 will be about 0.25 inches, and the baffles 3 will be about 5 feet apart.

Fig. 4 shows a modified form of fender F', which has a generally D-shaped cross-section.

This modified fender F' is intended for use with a larger, more conventional vessel than an RIB, for example as illustrated in Fig. 5.

The fender F' is formed in the same manner as the fender F of Figs. 1 to 3, but includes the additional step of fixing the additional pieces la (which help define the D-shape of the fender) to the annular sections prior to these sections being joined together.

The type of fender described above does not suffer from the disadvantages of the prior art fenders. In particular, because the fenders of the present invention are not filled with pressurised air, there is substantially no loss of buoyancy or impact-protection in the unlikely event of being punctured. This is enhanced by the fact that the layer 1 of foam has memory properties. Thus, the step of bending a sheet of polyethylene closed cell foam round a cylindrical former deforms the closed cell structure in such a way that the foam subsequently tries to retain this annular shape. Consequently, if the fender is split open, the memory of the layer 1 forces the split ends together, thereby substantially preventing the ingress of water into the fender.

Obviously, the layer 1 of foam is itself buoyant, and the relatively large volume of air trapped in the fender increases this buoyancy.

The relatively thin elastomer coating 2 does reduce the buoyancy of the fender slightly, but has the important advantage of being very tough, and so provides powerful impact protection to the relatively fragile foam layer 1.

The elastomer coating 2 has the additional advantage that it deters the growth of algae, so fenders of this type tend to stay much cleaner in use than known fenders.

It will be apparent that the type of fender described above could be used in many other marine applications in addition to its use as a sponson for an RIB. Thus, it could be used as fendering for all sizes of ships and small boats, as well as at mooring points. In this latter case, the fender may contain a gas at a pressure which would cause the fender to become slighly negatively buoyant. In this case, the fender will be able to assume a "floating" position beneath the water surface so as to protect against impacts with vessels which have their widest part beneath the water level.

This type of fender could also be used as a bumper for a motor vehicle, or for the protection of delicate cargoes during handling operations.

Claims (21)

1. A fender constituted by a closed envelope filled with a gas at substantially atmospheric pressure, the envelope being made of a laminated material which comprises an outer layer made of a hard, resilient, shock-absorbing material and an inner layer made of a compressible, shock-wave-damping material.

2. A fender as claimed in claim 1, wherein the outer layer is relatively thin, and the inner layer is relatively thick.

3. A fender as claimed in claim 1 or claim 2, wherein the inner layer is made of a closed cell foam material.

4. A fender as claimed in claim 3, wherein the foam material is a memory foam.

5. A fender as claimed in claim 3 or claim 4, wherein the foam material is a polyethylene foam.

6. A fender as claimed in any one of claims 1 to 5, wherein the outer layer is made of an elastomer material.

7. A fender as claimed in claim 6, wherein theelastomer is a polyurethane elastomer.

8. A fender as claimed in any one of claims 1 to 7, wherein the gas is air.

9. A fender as claimed in any one of claims 1 to 8, wherein the envelope has a generally annular cross-section.

10. A fender as claimed in any one of claims 1 to 9, further comprising a plurality of longitudinally-spaced, transverse baffles positioned within the envelope.

11. A fender as claimed in claim 10, wherein the baffles are made of the same material as the inner layer.

12. A fender as claimed in any one of claims 1 to 11, further comprising fixing straps for fixing the fender to a structure to be protected against impacts, the fixing straps being encapsulated within the outer layer.

13. A fender as claimed in claim 12 when appendant to claim 10, wherein each of the fixing straps is positioned to overlie a respective baffle.

14. A fender substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

15. A method of making a fender, having a closed envelope filled with a gas at substantially atmospheric pressure, the method comprising the steps of forming an inner envelope layer made of a compressible shock-wavedamping material, filling the inner envelope layer with a gas at the required pressure, and bonding an outer envelope layer to the inner envelope layer, the outer envelope layer being made of a hard, resilient, shock-absorbing material.

16. A method as claimed in claim 15, wherein the inner layer is formed in cylindrical sections from a closed cell foam material, the sections being heat-sealed or bonded together.

17. A method as claimed in claim 16, wherein each of said sections is made by bending a sheet of closed cell foam material around a former, and by heat-sealing or bonding the edges of the sheet together.

18. A method as claimed in claim 16 or 17, further comprising the step of heat sealing or bonding longitudinally-spaced, transverse baffles within the inner layer, the baffles being made of the same material as the inner layer.

19. A method as claimed in any one of claims 15 to 18, wherein the outer layer is an elastomer which is sprayed onto the inner layer.

20. A method as claimed in claim 19, further comprising the step of encapsulating fixing straps within the outer layer, the outer layer being formed from a plurality of sprayedon coats, and the straps being positioned between two adjacent sprayed-on coats.

21. A method of making a fender substantially as hereinbefore described with reference to the accompanying drawings.